Efficient communication of network identifiers

ABSTRACT

There is provided a method of operating a terminal device in a first network, the method comprising maintaining one or more indices and a mapping between the one or more indices and respective network identifiers, each network identifier identifying a network and/or a network node, wherein two or more networks and/or network nodes share the same index; and in the event that the terminal device is to take an action in respect of a network and/or network node having an index shared with another network and/or network node, the method further comprises the step of determining which one of the two or more networks and/or network nodes having the shared index the terminal device is to take the action in respect of. Methods of operating a node and network nodes are also provided.

TECHNICAL FIELD

The techniques described herein relate to the communication of networkidentifiers, for example identifiers of wireless local area networks,WLANs, between a terminal device and a network node, or between networknodes.

BACKGROUND

The wireless local-area network (WLAN) technology known as “Wi-Fi” hasbeen standardized by IEEE in the 802.11 series of specifications (i.e.,as “IEEE Standard for Information technology—Telecommunications andinformation exchange between systems. Local and metropolitan areanetworks—Specific requirements. Part 11: Wireless LAN Medium AccessControl (MAC) and Physical Layer (PHY) Specifications”).

Cellular operators that are currently serving mobile users with, forexample, any of the technologies standardized by the 3rd-GenerationPartnership Project (3GPP), including the radio-access technologiesknown as Long-Term Evolution (LTE), Universal Mobile TelecommunicationsSystem (UMTS)/Wideband Code-Division Multiple Access (WCDMA), High SpeedPacket Access (HSPA) and Global System for Mobile Communications (GSM),see Wi-Fi as a wireless technology that can provide good additionalsupport for users in their regular cellular networks. There is interestaround using the Wi-Fi technology as an extension, or alternative tocellular radio access network technologies to handle the alwaysincreasing wireless bandwidth demands. The term “operator-controlledWi-Fi” points to a Wi-Fi deployment that on some level is integratedwith a cellular network operator's existing network and where the 3GPPradio access networks and the Wi-Fi wireless access may even beconnected to the same core network and provide the same services.

3GPP is currently working on specifying a feature/mechanism forWLAN/3GPP Radio interworking which improves operator control withrespect to how a UE performs access selection and traffic steeringbetween 3GPP and WLANs belonging to the operator or its partners. Threedifferent solutions have been described in 3GPP TR 37.834 v12.0.0(2013-December) “Study on Wireless Local Area Network (WLAN)—3GPP radiointerworking (Release 12)”.

In one of the solutions (Solution 2 in TR 37.834), which is alsoreferred to as the “threshold-based mechanism” herein, the 3GPP network(i.e. network node of the first RAT) provides to the UE (the term usedto refer to a terminal device by 3GPP) conditions and/or thresholdswhich are used by the UE in one or more pre-defined rules dictating whenthe terminal device should steer traffic from one RAT to the other.

In another one of the solutions (Solution 3 in TR 37.834), which is alsoreferred to a “traffic steering command based mechanism” herein, the(3GPP) network configures the UE to send measurement reports related toWLANs the terminal device has discovered (or to WLANs for which certainconditions have been fulfilled). The network would, based on thesemeasurement reports, decide whether the terminal device shall steertraffic towards the reported WLANs. If a terminal device is to steertraffic towards a WLAN, the network sends a traffic steering command tothat terminal device.

In both of the above solutions, identifiers of WLANs (also referred toas WLAN identifiers) may need to be communicated between the radioaccess network, RAN, and the UE. In the threshold-based mechanism, theRAN may communicate a list of WLAN identifiers to the UE that areacceptable for the UE to consider when evaluating the pre-defined rules.In the traffic steering command based mechanism, the RAN may communicatea list of WLAN identifiers to the UE that the UE is to measure, and theUE may communicate the identity of one or more WLANs (i.e. the WLANidentifiers) that fulfill the conditions to the RAN.

WLAN identifiers are large, for example, a Service Set Indicator (SSID)may be up to 32 bytes. The communication of the WLAN identifiers betweenthe RAN and UE (and between nodes in the network in the event that theWLAN identifier list is provided from one node to another) can thereforegenerate a lot of signaling between the network and the UE just toidentify WLANs. This signaling will decrease system capacity, increaseterminal device power consumption, generate interference, etc.

A similar problem exists for other types of WLAN identifiers, such basicSSIDs, BSSIDs, extended SSIDs, ESSIDs, homogenous ESSIDs, HESSIDs, Realmidentifiers, Network Access Indicators, NAIs, public land mobilenetwork, PLMN, identifiers, or Domain Name lists, as well as identifiersfor networks operating according to other radio access technologies(RATs).

It will be appreciated that these problems are not confined to thecommunication of network identifiers as part of an interworkingmechanism, and that they can arise in other situations where one or morenetwork identifiers are communicated between a UE and network node (orbetween network nodes).

Therefore, there is a need for a technique for the efficientcommunication of network identifiers, for example identifiers of WLANs,between a terminal device and a network node, or between network nodes.

SUMMARY

According to a first aspect, there is provided a method of operating aterminal device in a first network, the method comprising maintainingone or more indices and a mapping between the one or more indices andrespective network identifiers, each network identifier identifying anetwork and/or a network node, wherein two or more networks and/ornetwork nodes share the same index; and in the event that the terminaldevice is to take an action in respect of a network and/or network nodehaving an index shared with another network and/or network node, themethod further comprises the step of determining which one of the two ormore networks and/or network nodes having the shared index the terminaldevice is to take the action in respect of.

According to a second aspect, there is provided a terminal device foruse in a first network, the terminal device being adapted to maintainone or more indices and a mapping between the one or more indices andrespective network identifiers, each network identifier identifying anetwork and/or a network node, wherein two or more networks and/ornetwork nodes share the same index; and determine which one of the twoor more networks and/or network nodes having the shared index theterminal device is to take an action in respect of in the event that theterminal device is to take an action in respect of a network and/ornetwork node having an index shared with another network and/or networknode.

According to a third aspect, there is provided a method of operating anode in a first network, the method comprising maintaining one or moreindices and a mapping between the one or more indices and respectivenetwork identifiers in an array or a table, each network identifieridentifying a network and/or a network node; and in communicationsbetween the node and another node in the first network in which aparticular network and/or a particular network node is to be identified,using the index associated with the particular network and/or theparticular network node to identify the particular network and/or theparticular network node.

According to a fourth aspect, there is provided a node for use in afirst network, the node being adapted to maintain one or more indicesand a mapping between the one or more indices and respective networkidentifiers in an array or a table, each network identifier identifyinga network and/or a network node; and use the index associated with theparticular network and/or the particular network node to identify theparticular network and/or the particular network node in communicationsbetween the node and another node in the first network in which aparticular network and/or a particular network node is to be identified.

According to a fifth aspect, there is provided a method of operating anetwork node in a first network, the method comprising determining oneor more indices and a mapping between the one or more indices andrespective network identifiers, each network identifier identifying anetwork and/or a network node, wherein different mappings are determinedfor different terminal devices and/or network subscribers; and sendingthe one or more indices and the mapping to another network node in thefirst network or to a terminal device in the first network.

According to a sixth aspect, there is provided a network node for use ina first network, the network node being adapted to determine one or moreindices and a mapping between the one or more indices and respectivenetwork identifiers, each network identifier identifying a networkand/or a network node, wherein different mappings are determined fordifferent terminal devices and/or network subscribers; and send the oneor more indices and the mapping to another network node in the firstnetwork or to a terminal device in the first network.

According to a seventh aspect, there is provided a method of operating anetwork node in a first network, the method comprising maintaining oneor more indices and one or more mappings between the one or more indicesand respective network identifiers, each network identifier identifyinga network and/or a network node, wherein different mappings apply todifferent terminal devices and/or network subscribers; and incommunications between the network node and a terminal device in which aparticular network and/or a particular network node is to be identified,using the index associated with the particular network and/or theparticular network node in the mapping that applies to the terminaldevice to identify the particular network and/or the particular networknode.

According to an eighth aspect, there is provided a network node for usein a first network, the network node being adapted to maintain one ormore indices and one or more mappings between the one or more indicesand respective network identifiers, each network identifier identifyinga network and/or a network node, wherein different mappings apply todifferent terminal devices and/or network subscribers; and use the indexassociated with the particular network and/or the particular networknode in the mapping that applies to a terminal device to identify aparticular network and/or a particular network node in communicationsbetween the network node and the terminal device in which the particularnetwork and/or the particular network node is to be identified.

According to a ninth aspect, there is provided a computer programproduct comprising a computer readable medium having computer readablecode embodied therein, the computer readable code being configured suchthat, on execution by a suitable computer or processor, the computer orprocessor is caused to perform any of the method embodiments describedabove.

According to a tenth aspect, there is provided a terminal device for usein a first network, wherein the terminal device comprises a processorand a memory, said memory containing instructions executable by saidprocessor whereby said terminal device is operative to maintain one ormore indices and a mapping between the one or more indices andrespective network identifiers, each network identifier identifying anetwork and/or a network node, wherein two or more networks and/ornetwork nodes share the same index; and determine which one of the twoor more networks and/or network nodes having the shared index theterminal device is to take an action in respect of in the event that theterminal device is to take an action in respect of a network and/ornetwork node having an index shared with another network and/or networknode.

According to an eleventh aspect, there is provided a terminal device foruse in a first network, the terminal device comprising a first modulefor maintaining one or more indices and a mapping between the one ormore indices and respective network identifiers, each network identifieridentifying a network and/or a network node, wherein two or morenetworks and/or network nodes share the same index; and a second modulefor determining which one of the two or more networks and/or networknodes having the shared index the terminal device is to take an actionin respect of in the event that the terminal device is to take an actionin respect of a network and/or network node having an index shared withanother network and/or network node.

According to a twelfth aspect, there is provided a node for use in afirst network, the node comprising a processor and a memory, said memorycontaining instructions executable by said processor whereby said nodeis operative to maintain one or more indices and a mapping between theone or more indices and respective network identifiers in an array or atable, each network identifier identifying a network and/or a networknode; and use the index associated with the particular network and/orthe particular network node to identify the particular network and/orthe particular network node in communications between the node andanother node in the first network in which a particular network and/or aparticular network node is to be identified.

According to a thirteenth aspect, there is provided a node for use in afirst network, the node comprising a first module for maintaining one ormore indices and a mapping between the one or more indices andrespective network identifiers in an array or a table, each networkidentifier identifying a network and/or a network node; and a secondmodule for using the index associated with the particular network and/orthe particular network node to identify the particular network and/orthe particular network node in communications between the node andanother node in the first network in which a particular network and/or aparticular network node is to be identified.

According to a fourteenth aspect, there is provided a network node foruse in a first network, the network node comprising a processor and amemory, said memory containing instructions executable by said processorwhereby said network node is operative to determine one or more indicesand a mapping between the one or more indices and respective networkidentifiers, each network identifier identifying a network and/or anetwork node, wherein different mappings are determined for differentterminal devices and/or network subscribers; and send the one or moreindices and the mapping to another network node in the first network orto a terminal device in the first network.

According to a fifteenth aspect, there is provided a network node foruse in a first network, the network node comprising a first module fordetermining one or more indices and a mapping between the one or moreindices and respective network identifiers, each network identifieridentifying a network and/or a network node, wherein different mappingsare determined for different terminal devices and/or networksubscribers; and a second module for sending the one or more indices andthe mapping to another network node in the first network or to aterminal device in the first network.

According to a sixteenth aspect, there is provided a network node foruse in a first network, the network node comprising a processor and amemory, said memory containing instructions executable by said processorwhereby said network node is operative to maintain one or more indicesand one or more mappings between the one or more indices and respectivenetwork identifiers, each network identifier identifying a networkand/or a network node, wherein different mappings apply to differentterminal devices and/or network subscribers; and use the indexassociated with the particular network and/or the particular networknode in the mapping that applies to a terminal device to identify aparticular network and/or a particular network node in communicationsbetween the network node and the terminal device in which the particularnetwork and/or the particular network node is to be identified.

According to a seventeenth aspect, there is provided a network node foruse in a first network, the network node comprising a first module formaintaining one or more indices and one or more mappings between the oneor more indices and respective network identifiers, each networkidentifier identifying a network and/or a network node, whereindifferent mappings apply to different terminal devices and/or networksubscribers; and a second module for using the index associated with theparticular network and/or the particular network node in the mappingthat applies to a terminal device to identify a particular networkand/or a particular network node in communications between the networknode and the terminal device in which the particular network and/or theparticular network node is to be identified.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the techniques introduced in this document aredescribed below with reference to the following figures, in which:

FIG. 1 is a non-limiting example block diagram of an LTE cellularcommunications network;

FIG. 2 is a block diagram of a terminal device according to anembodiment;

FIG. 3 is a block diagram of a radio access network node according to anembodiment;

FIG. 4 is a block diagram of a core network node according to anembodiment;

FIG. 5 is a block diagram of a WLAN access point according to anembodiment;

FIG. 6 illustrates an exemplary method of operating a terminal device;

FIG. 7 illustrates an exemplary method of operating a network node;

FIG. 8 illustrates another exemplary method of operating a network node;

FIG. 9 is a diagram illustrating one example of a network interworkingfeature;

FIG. 10 is a flow chart illustrating a method of operating a terminaldevice according to an embodiment;

FIG. 11 is a flow chart illustrating a method of operating a networknode according to another embodiment;

FIG. 12 is a flow chart illustrating a method of operating a networknode according to an embodiment;

FIG. 13 is a flow chart illustrating a method of operating a nodeaccording to another embodiment; and

FIG. 14 is a flow chart illustrating a specific embodiment of thetechniques described herein.

DETAILED DESCRIPTION

The following sets forth specific details, such as particularembodiments for purposes of explanation and not limitation. But it willbe appreciated by one skilled in the art that other embodiments may beemployed apart from these specific details. In some instances, detaileddescriptions of well known methods, nodes, interfaces, circuits, anddevices are omitted so as not obscure the description with unnecessarydetail. Those skilled in the art will appreciate that the functionsdescribed may be implemented in one or more nodes using hardwarecircuitry (e.g., analog and/or discrete logic gates interconnected toperform a specialized function, ASICs, PLAs, etc.) and/or using softwareprograms and data in conjunction with one or more digitalmicroprocessors or general purpose computers. Nodes that communicateusing the air interface also have suitable radio communicationscircuitry. Moreover, the technology can additionally be considered to beembodied entirely within any form of computer-readable memory, such assolid-state memory, magnetic disk, or optical disk containing anappropriate set of computer instructions that would cause a processorand also in some cases a receiver component and/or transmitter componentto carry out the techniques described herein.

Hardware implementation may include or encompass, without limitation,digital signal processor (DSP) hardware, a reduced instruction setprocessor, hardware (e.g., digital or analog) circuitry including butnot limited to application specific integrated circuit(s) (ASIC) and/orfield programmable gate array(s) (FPGA(s)), and (where appropriate)state machines capable of performing such functions.

In terms of computer implementation, a computer is generally understoodto comprise one or more processors, one or more processing units, one ormore processing modules or one or more controllers, and the termscomputer, processor, processing unit, processing module and controllermay be employed interchangeably. When provided by a computer, processor,processing unit, processing module or controller, the functions may beprovided by a single dedicated computer, processor, processing unit,processing module or controller, by a single shared computer, processor,processing unit, processing module or controller, or by a plurality ofindividual computers, processors, processing units, processing modulesor controllers, some of which may be shared or distributed. Moreover,the terms “processor”, “processing unit”, “processing module” or“controller” also refer to other hardware capable of performing suchfunctions and/or executing software, such as the example hardwarerecited above.

Although the description is given for a terminal device or userequipment (UE), it should be understood by the skilled in the art that“terminal device” and “UE” are non-limiting terms comprising any mobile,non-mobile or wireless device or node equipped with a radio interfaceallowing for at least one of: transmitting signals in uplink (UL) andreceiving and/or measuring signals in downlink (DL). A UE herein maycomprise a UE (in its general sense) capable of operating or at leastperforming measurements in one or more frequencies, carrier frequencies,component carriers or frequency bands. It may be a “UE” operating insingle- or multi-radio access technology (RAT) or multi-standard mode.As well as “UE” and “terminal device”, the term “mobile device” is usedinterchangeably in the following description, and it will be appreciatedthat such a device does not necessarily have to be mobile in the sensethat it is carried by a user. Instead, the term “mobile device”, as with“terminal device” encompasses any device that is capable ofcommunicating with communication networks that operate according to oneor more mobile communication standards, such as GSM, UMTS, LTE, etc.

A cell is associated with a radio access network (RAN) node, where a RANnode comprises in a general sense any node transmitting radio signals inthe downlink (DL) to a terminal device and/or receiving radio signals inthe uplink (UL) from a terminal device. Some example RAN nodes, or termsused for describing RAN nodes, are base station, eNodeB, eNB, NodeB,macro/micro/pico/femto radio base station, home eNodeB (also known asfemto base station), relay, repeater, sensor, transmitting-only radionodes or receiving-only radio nodes. A RAN node may operate or at leastperform measurements in one or more frequencies, carrier frequencies orfrequency bands and may be capable of carrier aggregation. It may alsobe a single-radio access technology (RAT), multi-RAT, or multi-standardnode, e.g., using the same or different base band circuitry fordifferent RATs.

It should be noted that unless otherwise indicated, the use of thegeneral term “network node” as used herein refers to a RAN node, such asa base station, an eNodeB, a network node in the RAN responsible forresource management, such as a radio network controller (RNC), a corenetwork node, such as a mobility management entity (MME) or servinggateway (SGW), or a WLAN Access Point (AP).

The signalling described is either via direct links or logical links(e.g. via higher layer protocols and/or via one or more network nodes).For example, signalling from a coordinating node may pass anothernetwork node, e.g., a radio node.

FIG. 1 shows an example diagram of an evolved UMTS Terrestrial RadioAccess Network (EUTRAN) architecture as part of an LTE-basedcommunications system 2. Nodes in the core network 4 include one or moreMobility Management Entities (MMEs) 6, a key control node for the LTEaccess network, and one or more Serving Gateways (SGWs) 8 which routeand forward user data packets while acting as a mobility anchor. Theycommunicate with base stations 10 in the RAN referred to in

LTE as eNBs or eNodeBs, over an interface, for example an S1 interface.The eNBs 10 can include the same or different categories of eNBs, e.g.macro eNBs, and/or micro/pico/femto eNBs. The eNBs 10 communicate witheach other over an interface, for example an X2 interface. The S1interface and X2 interface are defined in the LTE standard. A UE 12 canreceive downlink data from and send uplink data to one of the basestations 10 with that base station 10 being referred to as the servingbase station of the UE 12. An access point (AP) 14 that is part of aWLAN is also shown in FIG. 1, although it will be appreciated that theWLAN and AP 14 are not part of the EUTRAN architecture.

FIG. 2 shows a terminal device 12 or user equipment (UE) that can beadapted for use in one or more of the non-limiting example embodimentsdescribed. The terminal device 12 comprises a processing unit 30 thatcontrols the operation of the terminal device 12. The processing unit 30is connected to a receiver or a transceiver 32 (which comprises areceiver and a transmitter) with associated antenna(s) 34 which are usedto receive signals from or both transmit signals to and receive signalsfrom one or more different types of radio access network (e.g. two ormore radio access networks that are operating according to differentradio access technologies, RATs), such as RAN node 10 in the LTE network2 and access point (AP) 14 in a WLAN. The terminal device 12 alsocomprises a memory unit 36 that is connected to the processing unit 30and that stores computer program code and other information and datarequired for the operation of the terminal device 12.

FIG. 3 shows a RAN node 10 (for example a base station, NodeB or aneNodeB) that can be adapted for use in example embodiments described.The RAN node 10 comprises a processing unit 40 that controls theoperation of the base station 10. The processing unit 40 is connected toa transmitter or a transceiver 42 (which comprises a receiver and atransmitter) with associated antenna(s) 44 which are used to transmitsignals to, and receive signals from, terminal devices 12 in the network2. The RAN node 10 also comprises a memory unit 46 that is connected tothe processing unit 40 and that stores computer program code and otherinformation and data required for the operation of the RAN node 10. TheRAN node 10 also includes components and/or circuitry 48 for allowingthe RAN node 10 to exchange information with other RAN nodes 10 (forexample via an X2 interface) and components and/or circuitry 49 forallowing the RAN node 10 to exchange information with nodes in the corenetwork 4 (for example via the S1 interface). It will be appreciatedthat RAN nodes for use in other types of network (e.g. UTRAN or WCDMARAN) may include similar components to those shown in FIG. 3 and may, ifappropriate, include interface circuitry 48, 49 for enablingcommunications with the other network nodes in those types of networks(e.g. other base stations, mobility management nodes and/or nodes in thecore network).

FIG. 4 shows a core network node 6, 8 that can be adapted for use in theexample embodiments described. The node 6, 8 comprises a processing unit50 that controls the operation of the node 6, 8. The processing unit 50is connected to components and/or circuitry 52 for allowing the node 6,8 to exchange information with RAN nodes 10 with which it is associated(which is typically via the S1 interface). The node 6, 8 also comprisesa memory unit 56 that is connected to the processing unit 50 and thatstores computer program code and other information and data required forthe operation of the node 6, 8.

FIG. 5 shows a WLAN AP 14 that can be adapted for use in the exampleembodiments described. The AP 14 comprises a processing unit 60 thatcontrols the operation of the AP 14. The processing unit 60 is connectedto a transmitter or a transceiver 62 (which comprises a receiver and atransmitter) with associated antenna(s) 64 which are used to transmitsignals to, and receive signals from, terminal devices 12. The AP 14also comprises a memory unit 66 that is connected to the processing unit60 and that stores computer program code and other information and datarequired for the operation of the AP 14. The AP 14 also includescomponents and/or circuitry 68 for connecting the AP 14 to a telephoneline or other broadband connection.

It will be appreciated that only the components of the terminal device12, RAN node 10, core network node 6, 8 and AP 14 that are useful toexplain the embodiments presented herein are illustrated in FIGS. 2, 3,4 and 5.

As noted above, it is often useful or required to communicate networkidentifiers, which identify a particular network or a particular networknode (such as an eNB or WLAN AP), between a terminal device and anetwork node, or between network nodes. These network identifiers caninclude identifiers used in WLANs (i.e. WLAN identifiers), such as aService Set Indicator (SSID), a basic SSID, BSSID, an extended SSID,ESSID, a homogenous ESSID, HESSID, a Realm identifier, a Network AccessIndicator, NAI, a public land mobile network, PLMN, identifier, or aDomain Name list, as well as identifiers for networks operatingaccording to other radio access technologies (RATs). It will beappreciated that some network identifiers identify both a network and aparticular network node. For example a HESSID identifies both a networkand a particular WLAN. A HESSID is the BSSID of a certain WLAN AP in agroup of APs, and the BSSID of this selected WLAN AP is also used toidentify the group of APs.

Since these network identifiers can be quite large, for example, aService Set Indicator (SSID) may be up to 32 bytes, and it may often benecessary to communicate a number of network identifiers, it isdesirable for there to be a technique for the efficient communication ofnetwork identifiers between a terminal device and a network node orbetween network nodes, in order to minimise the signalling required andavoid unnecessarily decreasing system capacity, increasing terminaldevice power consumption and generating interference.

Thus according to the techniques described herein, to reduce the amountof signaling between the network node and the terminal device (andbetween network nodes) an identifier-to-index mapping is introduced sothat the indices can be signaled instead of explicitly signaling thenetwork identifiers.

In this technique, a mapping between network identifiers and indices isdetermined. This mapping can be determined by a network node in theradio access network (RAN) or core network (CN), such as aneNB/RNC/MME/etc. The network node can then signal this mapping to aterminal device and/or other network nodes (e.g. from a CN node to oneor more RAN nodes, or from a RAN node to other RAN nodes). The indicesprovided by the mapping can then be used in communications between thenetwork and the terminal device or between network nodes, which avoidhaving to use the network identifiers themselves in the communications.The indices act as a ‘common language’ between the network and theterminal or between the network nodes.

FIG. 6 illustrates an exemplary method of operating a terminal device.Thus, in a first step, step 101, the terminal device 12 maintains one ormore indices and a mapping between the one or more indices andrespective network identifiers. Each of the network identifiersidentifies a network and/or a network node. The indices and mapping canbe maintained by storing them in the memory unit 36 of the terminaldevice 12 or reading them from broadcast or dedicated signalling fromthe network.

The network identifiers preferably relate to network(s) and/or networknodes in a network other than the first network 2 (although in someembodiments they can relate to network nodes in the same network). Thenetwork and/or network nodes can be operating according to the same or adifferent RAT to the first network 2.

The indices and mapping maintained in step 101 may have been receivedfrom the first network 2. In other implementations, the terminal device12 may receive a list and/or sequence of network identifiers from thefirst network 2 and determine the one or more indices and the mappingbased on the position of each network identifier in the received listand/or sequence.

Various different implementations relating to the form of the indicesand mapping are described in more detail below.

After maintaining (e.g. storing or reading) the one or more indices andthe mapping, in communications between the terminal device 12 and afirst network 2 in which a particular network and/or a particularnetwork node (e.g. WLAN AP 14) is to be identified, the terminal device12 uses the index associated with the particular network and/or theparticular network node to identify the particular network and/or theparticular network node (step 103). As described in more detail below,these communications can comprise downlink communications from the firstnetwork 2 that include an index or indices relating to one or morenetworks and/or network nodes to be identified to the terminal device12, uplink communications from the terminal device 12 to the firstnetwork 2 that include an index or indices relating to one or morenetworks and/or network nodes to be identified to the first network 2,or both uplink and downlink communications.

FIG. 7 illustrates an exemplary method of operating a network node 10 ofa first network 2. The network node may be a node in the RAN of thefirst network (in which case the network node can be an eNB, RNC or WLANAP). In a first step, step 111, the network node 10 maintains one ormore indices and a mapping between the one or more indices andrespective network identifiers. Each of the network identifiersidentifies a network and/or a network node (e.g. an eNB or WLAN AP). Theindices and mapping can be maintained by storing them in the memory unit46 of the network node 10.

The network identifiers preferably relate to network(s) and/or networknodes in a network other than the first network 2 (although in someimplementations they can relate to network nodes in the same network).The network and/or network nodes can be operating according to the sameor a different RAT to the first network 2.

The indices and mapping maintained in step 111 may have been receivedfrom a network node 6 in the core network 4 the first network 2 oranother network node 10 in the RAN. In other implementations, thenetwork node 10 may determine the one or more indices and mapping from alist and/or sequence of network identifiers.

Various different implementations relating to the form of the indicesand mapping are described in more detail below.

After maintaining the one or more indices and mapping, in communicationsbetween the network node 10 and a terminal device 12 or another networknode 10 in which a particular network and/or a particular network nodeis to be identified, the network node 10 uses the index associated withthe particular network and/or the particular network node to identifythe particular network and/or the particular network node (step 113). Asdescribed in more detail below, these communications can comprisedownlink communications from the network node 10 to the terminal device12 that include an index or indices relating to one or more networksand/or network nodes to be identified to the terminal device 12, uplinkcommunications from the terminal device 12 to the network node 10 thatinclude an index or indices relating to one or more networks and/ornetwork nodes to be identified to the first network 2 by the terminaldevice 12, or both uplink and downlink communications.

In some implementations, a network node may be responsible fordetermining the one or more indices and mapping and providing these toother network nodes. A method of operating a network node according tothis implementations is shown in FIG. 8. This method may be performed ina RAN node 10, such as an eNB, RNC or WLAN AP, or a node 6 in the corenetwork 4, such as an MME.

Thus, in step 121, the network node 6 determines one or more indices anda mapping between the one or more indices and respective networkidentifiers. Each of the network identifiers identifies a network and/ora network node (e.g. an eNB or WLAN AP).

The network identifiers may relate to network(s) and/or network nodes ina network other than the network in which the network node 6 isoperating, but in other embodiments they can relate to network nodes inthe same network.

The network node 6 then sends the one or more indices and the mapping toa network node 10, for example in the RAN of the network, and/or to aterminal device 12 in the network (step 123).

In the following explanation of the techniques provided herein, thespecific example of WLAN identifiers is used, but it will be appreciatedthat the techniques described below are equally applicable to othertypes of network identifiers.

In the following various implementations are described of how a networknode associates an index to a network (e.g. WLAN) identifier (whichherein will be referred to as identifier-to-index mapping) aredescribed, how a network node communicates these indices and the mappingto the terminal device or to another network node, and how the index canbe used in communications between the network node and the terminaldevices to reduce signaling overhead.

As noted above the network node sending this mapping may be an eNB, NB,RNC or similar. As noted above in FIG. 8, in some implementations onenetwork node assigns the indices to the identifiers and this assignmentis then used by other network nodes. For example, it will be describedbelow how an MME establishes the identifier to index mapping, and themapping is used by another network node such as an eNB in itscommunication with a terminal device.

Although the identifier-to-index mapping is not limited to use inspecific situations, protocols or mechanisms, the following descriptionof the identifier-to-index mapping relates to its use in a 3GPP/WLANinterworking mechanism. The interworking mechanism may relate to any oneor more of access network selection, traffic steering (where all of auser's traffic or a certain part of a user's traffic is steered to aparticular network) and aggregation (where a user's traffic may be splitbetween carriers with networks operating according to different RATs,e.g. a carrier to a WLAN and a carrier to a 3GPP network). Thus, oneexemplary use of the techniques is where a 3GPP network node (i.e. anetwork node in a 3GPP network), such as an eNB, signals WLANidentifiers to a terminal device. The eNB may associate an index orindices with the WLAN identifiers and signal this mapping to theterminal device. This mapping can then be used in communication betweenthe network and the terminal device by referring to the indices insteadof the WLAN identifiers.

Two exemplary interworking mechanisms in which the techniques can beapplied, the threshold-based mechanism and traffic steering commandbased mechanism mentioned above, are described in more detail below.These mechanisms/solutions are described in 3GPP TR 37.834 v12.0.0(2013-December) “Study on Wireless Local Area Network (WLAN)—3GPP radiointerworking (Release 12)” as Solutions 2 and 3 respectively.

Solution 2

As noted above, in the threshold based mechanism the 3GPP network (i.e.network node of the first RAT) provides to the UE conditions and/orthresholds which are used by the UE in one or more pre-defined rulesdictating when the terminal device should steer traffic from one RAT tothe other.

For example, a pre-defined rule could be of the form shown in Table 1where threshold1, threshold2, threshold3 and threshold4 are provided tothe UE by the 3GPP network, i.e. a network node of the first RAT such asan eNodeB, Node B or RNC.

TABLE 1 Example of the threshold based mechanism if (3GPP signal <threshold1) && (WLAN signal > threshold2) {   steerTrafficToWLAN( ); }else if (3GPP signal > threshold3) || (WLAN signal < threshold4) {  steerTrafficTo3gpp( ); }

This exemplary rule provides that if the UE measured 3GPP signal isbelow threshold1 and the UE measured WLAN signal is above threshold2then the terminal device steers traffic to WLAN. Otherwise, if the 3GPPsignal is above threshold3 and the WLAN signal is below threshold4 theterminal device steers traffic to 3GPP.

The term ‘3GPP signal’ herein could mean the signal transmitted by aradio network node belonging to a 3GPP RAT, e.g. a node in a LTE, HSPA,GSM etc. network, and/or it could be the quality of such a signal. Theterm ‘WLAN signal’ herein could mean the signal transmitted by a radionetwork node belonging to WLAN, e.g. an access point (AP) etc., and/orit could be the quality of such a signal. Examples of measurements of3GPP signals include are reference signal received power (RSRP) andreference signal received quality (RSRQ) in LTE or common pilot channel(CPICH) received signal code power (RSCP) and CPICH Ec/No in HSPA.Examples of measurements of WLAN signals are Received Signal StrengthIndicator (RSSI), Received Channel Power Indicator (RCPI), ReceivedSignal to Noise Indicator (RSNI), etc.

A high level description of this threshold based mechanism is providedbelow and also in 3GPP TS 36.300 v12.2.0

23.6 Access network selection and traffic steering between E-UTRAN andWLAN

This section describes the mechanisms to support traffic steeringbetween E-UTRAN and WLAN.

23.6.1 General Principles

This version of the specification supports E-UTRAN assisted UE basedbi-directional traffic steering between E-UTRAN and WLAN for UEs inRRC_IDLE and RRC_CONNECTED.

E-UTRAN provides assistance parameters via broadcast and dedicated RRCsignalling to the UE. The RAN assistance parameters may include E-UTRANsignal strength and quality thresholds, WLAN channel utilizationthresholds, WLAN backhaul data rate thresholds, WLAN signal strength andquality thresholds and Offload Preference Indicator (OPI). E-UTRAN canalso provide a list of WLAN identifiers to the UE via broadcastsignalling. WLANs provided by E-UTRAN may include an associatedpriority.

The UE uses the RAN assistance parameters in the evaluation of:

-   -   Traffic steering rules defined in TS 36.304 [11]; or    -   ANDSF policies defined in TS 24.312 [58]        for traffic steering decisions between E-UTRAN and WLAN as        specified in TS 23.402[19].

The OPI is only used in ANDSF policies as specified in TS 24.312 [58].

WLAN identifiers are only used in traffic steering rules defined in TS36.304 [11].

If the UE is provisioned with ANDSF policies it shall forward thereceived RAN assistance parameters to upper layers, otherwise it shalluse them in the traffic steering rules defined in section 23.6.2 and TS36.304 [11]. The traffic steering rules defined in section 23.6.2 and TS36.304 [11] are applied only to the WLANs of which identifiers areprovided by the E-UTRAN.

The UE in RRC_CONNECTED shall apply the parameters obtained viadedicated signalling if such have been received from the serving cell;otherwise, the UE shall apply the parameters obtained via broadcastsignalling.

The UE in RRC_IDLE shall keep and apply the parameters obtained viadedicated signalling, until cell reselection or a timer has expiredsince the UE entered RRC_IDLE upon which the UE shall apply theparameters obtained via broadcast signalling. In the case of RANsharing, each PLMN sharing the RAN can provide independent sets of RANassistance parameters.

23.6.2 Access Network Selection and Traffic Steering Rules

The UE indicates to upper layers when (and for which WLAN identifiersalong with associated priorities, if any) access network selection andtraffic steering rules defined in TS 36.304 [11] are fulfilled. Theselection among WLAN APs that fulfil the access network selection andtraffic steering rules is up to UE implementation.

When the UE applies the access network selection and traffic steeringrules defined in TS 36.304 [11], it performs traffic steering betweenE-UTRAN WLAN with APN granularity.

User preference takes precedence (FFS whether it does not apply toparticular scenarios).

Solution 3

As noted above, in the traffic steering command based mechanism, the(3GPP) network configures the terminal device to send measurementreports related to WLANs the terminal device has discovered (or to WLANsfor which certain conditions have been fulfilled). The network would,based on these measurement reports, decide whether the terminal deviceshall steer traffic towards the reported WLANs. If a terminal device isto steer traffic towards a WLAN, the network sends a traffic steeringcommand to that terminal device.

The following detailed description of this solution is also found insection 6.1.3 of TR 37.834:

In this solution the traffic steering for UEs in RRC CONNECTED/CELL_DCHstate is controlled by the network using dedicated traffic steeringcommands, potentially based also on WLAN measurements (reported by theUE).

For UEs in IDLE mode and CELL_FACH, CELL_PCH and URA_PCH states thesolution is similar to solution 1 or 2 [as described in TR 37.834].

Alternatively, UEs in those RRC [Radio Resource Control] states can beconfigured to connect to RAN and wait for dedicated traffic steeringcommands.

Overall description—As an example, traffic steering for UEs in RRCCONNECTED/CELL_DCH comprises the following steps as shown in FIG. 9.

Step 201. Measurement control: The eNB/RNC configures the UE measurementprocedures including the identity of the target WLAN to be measured.

Step 202. Measurement report: The UE is triggered to send MEASUREMENTREPORT by the rules set by the measurement control.

Step 203. Traffic steering: The eNB/RNC sends the steering commandmessage to the UE to perform the traffic steering based on the reportedmeasurements and loading in the RAN.

The above procedures do not take into account user preference and/or theWLAN radio state. For example, based on user preferences and/or WLANradio state, a UE may not be able to perform the configured measurementevents. Additionally, the procedures need to allow a UE to be able toprioritize non-operator WLAN over operator WLAN. For example, the UE maydisassociate from the operator WLAN and associate with the higherpriority non-operator WLAN at any time during the measurement process.

The procedure illustrated above, and the following description can applyto UMTS CELL_FACH as well. The procedure can also be extended toUMTS/LTE Idle modes and UMTS CELL/URA_PCH states, e.g. UEs may beconfigured to report some indication (e.g. on available WLANmeasurements) in a RRC UL message, e.g., RRC connection request (fromIdle, in UMTS/LTE) or CELL UPDATE (in UMTS CELL/URA_PCH states).

Some of the steps above, e.g. steps 201 & 202, can be optional, based onRAN/UE configuration.

Step 201: Measurement control—For measurement control, the followingexamples are types of information can be configured for the UE tomeasure the operator WLAN:

1. Measurement events to trigger reporting as defined in Table 2 below

2. Target identification as defined in Table 3 below

3. Measurements to report as defined in Table 4 below

Based on the measurement events defined in 3GPP TS 36.331 [“EvolvedUniversal Terrestrial Radio Access (E-UTRA); Radio Resource Control(RRC); Protocol specification”] and 3GPP TS 25.331 [“Radio ResourceControl (RRC); Protocol Specification”], Table 2 shows the candidatemeasurement events for WLAN:

TABLE 2 Candidate measurement events for reporting WLAN EventDescription W1 WLAN becomes better than a threshold (to trigger trafficsteering to WLAN) W2 WLAN becomes worse than a threshold (to triggertraffic steering from WLAN) W3 3GPP Cell's radio quality becomes worsethan threshold1 and WLAN's radio quality becomes better than threshold2(to trigger traffic steering to WLAN) W4 WLAN's radio quality becomesworse than threshold1 and 3GPP Cell's radio quality becomes better thanthreshold2 (to trigger traffic steering from WLAN)

The thresholds are based on the values of the measurements to reportdefined in Table 4 below.

The target identification is used to indicate to the UE which WLAN toconsider for the measurement control procedures including the targetWLAN ID and the operating channels to search for. Table 3 shows thecandidate target identifiers for WLAN.

For steering traffic from WLAN, i.e., W2/W4, it may be sufficient thatjust the serving WLAN below a threshold is reported, i.e. the WLANtarget identifiers are not needed.

TABLE 3 Candidate target identifiers for WLAN Availability IdentifierDescription in WLAN BSSID Basic Service Set Identifier: For Beacon orinfrastructure BSS, the BSSID is the MAC Probe address of the wirelessaccess point Response SSID Service Set Identifier: The SSID can beBeacon or used in multiple, possibly overlapping, Probe BSSs ResponseHESSID Homogeneous Extended Service Set Beacon or Identifier: A MACaddress whose value Probe shall be configured by the Hotspot OperatorResponse with the same value as the BSSID of one of (802.11) the APs inthe network. All APs in the wireless network shall be configured withthe same HESSID value. Domain Domain Name List element provides a listANQP Name List of one or more domain names of the entity (HS 2.0)operating the WLAN access network. Operating Indication of the targetWLAN frequency. N/A class, See Annex E of 802.11 [5] for channeldefinitions of the different number operating classes NOTE: If aboveinformation is not available in eNB/RNC, it is possible for RAN toconfigure general WLAN measurements

Step 202: Measurement report—Table 4 shows the candidate measurements toreport for WLAN.

TABLE 4 Candidate measurement to report for WLAN Availability IdentifierDescription in WLAN RCPI Received Channel Power Indicator: Measure ofthe received RF Measurement power in the selected channel for a receivedframe in the range of −110 to 0 dBm RSNI Received Signal to NoiseIndicator: An indication of the signal to Measurement noise plusinterference ratio of a received IEEE 802.11 frame. Defined by the ratioof the received signal power (RCPI-ANPI) to the noise plus interferencepower (ANPI) in steps of 0.5 dB in the range from −10 dB to +117 dB BSSContains information on the current STA population and traffic levelsBeacon or Load in the BSS. Probe Response (802.11k) WAN Includesestimates of DL and UL speeds and loading as well as link ANQP (HSmetrics status and whether the WLAN AP is at capacity. 2.0)

Step 203: Traffic steering—In order for RAN to control traffic routing(if agreed to be supported) if ANDSF [Access Network Discovery andSelection Function] is not used, the RAN would need to know which APNs[Access Point Names]/bearers may be (not) offloaded. The RAN also needsmeans to inform the UEs accordingly so that e.g. the UE can issue thecorresponding binding update with the CN over S2c. This would impactsignalling between CN and eNB as well as the UE behaviour between AS andNAS level. Table 5 shows candidate examples for identifying the trafficto steer to or from WLAN.

TABLE 5 Candidate identifiers of the traffic to steer to or from WLANIdentifier Description DRB/RB-ID Identity of a radio bearer QCI QoSClass Identifier

Establishing the mapping between network identifiers and indices

In some implementations the indices are numerical values. The index maytherefore be an integer value. Possible ranges are 0-15, 1-16, etc,although the range can depend on how many network identifiers there are.The mapping would then indicate the associated numerical value for eachWLAN identifier. One example how this mapping could be communicated froma network node 10 to a terminal device 12 in RRC is illustrated belowwhere the information element wlan-identifierindex indicates which indexthe associated identifier has:

WLAN-IdPerPLMN-r12 ::= SEQUENCE {  wlan-Identifiers CHOICE {   ssidOCTET STRING (SIZE (1..32)),   bssid OCTET STRING (SIZE (6)),   hessidOCTET STRING (SIZE (6))  },  wlan-identifierIndex INTEGER(1..maxWLAN-Id-r12)  OPTIONAL -- Need OR }

In some implementations a default index will be assigned by a terminaldevice 12 or other network node 10 to a WLAN identifier for which thenetwork has not provided an index. The index may then not need to besignaled to the terminal device 12 or the other network node 10 andadditional signaling overhead reduction can be achieved. An example howthis can be implemented in RRC is shown below where the value 0 is thedefault value for WLAN identifiers.

WLAN-IdPerPLMN-r12 ::= SEQUENCE {  wlan-Identifiers CHOICE {   ssidOCTET STRING (SIZE (1..32)),   bssid OCTET STRING (SIZE (6)),   hessidOCTET STRING (SIZE (6))  },  wlan-identifierIndex INTEGER(1..maxWLAN-Id-r12)  DEFAULT    0 }

This index may alternatively be an alphanumeric or alphabetic character.An example of how this can be implemented in RRC is shown below.

WLAN-IdPerPLMN-r12 ::= SEQUENCE {  wlan-Identifiers CHOICE {   ssidOCTET STRING (SIZE (1..32)),   bssid OCTET STRING (SIZE (6)),   hessidOCTET STRING (SIZE (6))  },  wlan-identifierIndex IA5String  OPTIONAL --Need OR }

In some implementations the mapping is implicit, and it is not necessaryfor a network node to explicitly signal the mapping and index associatedwith each identifier since a terminal device 12 or other network node 10will implicitly know the index of an identifier. One possible way ofimplementing implicit mapping is for the index to be determined based onthe position of the network identifier in a list and/or sequence. Forexample, a list and/or sequence of WLAN identifiers can be indicated inthe following order: SSID A, SSID B, SSID C. The indices could then bemapped as: SSID A has index 1 (or 0), SSID B has index 2 (or 1), SSID Chas index 3 (or 2).

In some implementations, the index can be signaled using a priorityindicator. The example below shows how a priority indicator can be used.The priority indicator would need to be signaled as a unique value foreach network identifier if it is to be possible to distinguish differentidentifiers (i.e. two WLAN identifiers cannot have the same priority).However, it would be possible for multiple WLAN identifiers to have thesame index (i.e. priority indicator in this implementation) in case itis acceptable that the identifiers which share a priority indicator aretreated similarly (e.g. the network sends a traffic steering commandwhich targets multiple WLANs).

WLAN-IdPerPLMN-r12 ::= SEQUENCE {  wlan-Identifiers CHOICE {   ssidOCTET STRING (SIZE (1..32)),   bssid OCTET STRING (SIZE (6)),   hessidOCTET STRING (SIZE (6))  },  wlan-Priority INTEGER (1..maxWLAN-Id-r12), OPTIONAL -- Need OR }

In some implementations the same index may be assigned to multiplenetwork identifiers. This could be done for networks or network nodesthat do not need to be treated or considered differently (for example inan access network selection and/or traffic steering mechanism). Forexample, if in a certain situation WLAN A and WLAN B can be treatedsimilarly those identifiers could be assigned the same index. However iftwo WLANs should be treated differently, then different indices could beassigned to the two WLANs (for example if one WLAN belongs to theoperator and the other WLAN belongs to the operator's partner and maycost more to use, then the operator may want to treat the WLANsdifferently and hence assign different indices to the two WLANs).

In some implementations multiple indices can be assigned to a networkidentifier. This allows a WLAN identifier to be assigned one index whichis common for multiple WLAN identifiers while also being assigned anindex which is unique to that WLAN identifier (or common to a smallergroup of identifiers). The benefit of this in an access networkselection and/or traffic steering mechanism is that the network 10 andterminal device 12 may use the index that is common for multiple WLANidentifiers (i.e. a low granular index) in situations where it is notimportant to distinguish those WLAN identifiers, while one uniqueidentifier could also be indicated by using a unique index (i.e. a highgranular index). For example, consider a scenario where the trafficsteering command based mechanism described above is used and the networkwants to perform offloading to WLAN for a terminal device. The networkmay then request the terminal device 12 perform measurements of multipleWLANs by using the low granular index (so that multiple WLANs aremeasured). The terminal device 12 would then report back to the networkin a measurement report; however in this measurement report it may beimportant to get measurements per WLAN identifier and hence the terminaldevice 12 could report the measurements and indicate the high granularindex.

Example 1 below shows one possible identifier-to-index mapping. In thisexample there are two identifiers (BSSID V and BSSID W) which have thesame index. This may be used for example if the two WLAN identifiershave some commonality such as belonging to the same SSID. The networkmay not need to distinguish between BSSID V and BSSID W if these belongto the same SSID. Example 1 also shows how each identifier can havemultiple indices (indicated by the additional index in the Index2column).

Example 1: WLAN identifier to index mapping WLAN identifier Index1Index2 BSSID U 1 A BSSID V 2 B BSSID W 2 C SSID X 3 D SSID Y 6 E

The mapping may be signaled to a terminal device 12 by a RAN node 10using broadcast signaling. Signaling the mapping with broadcastsignaling will ensure that it does not need to be signaled to eachterminal device 12 that needs to receive it, hence radio resources maybe saved.

Alternatively, the mapping may be signaled to the terminal device 12using dedicated signaling. The benefit of using dedicated signaling isthat different terminal devices may be provided with differentidentifier-to-index mappings which could allow for differentiation ofterminal devices 12.

In some implementations the mapping can be signaled to a terminal device12 by a core network node 6 such as an MME. The MME 6 can then informthe terminal device 12 of the mapping using non-access stratum (NAS)signaling. The MME 6 may also signal this mapping to the RAN node 10(e.g. to an eNB over the S1-interface) so that the RAN node 10 caninterpret a communication (e.g. a measurement report) containing indicesreceived from the terminal device 12.

In some implementations the identifier to index mapping can bepreconfigured in the terminal device 12. One example is that the indicesand mapping is provided to the terminal device 12 on a subscriberidentity module (SIM)-card or similar entity. Network nodes (e.g. in theRAN) could then be informed of the appropriate mapping, for example byoperations administration and management (OAM) configuration.

When the identifier-to-index mapping has been established and providedto the terminal device 12 and/or RAN node 10 the mapping can be used toreduce the amount of signaling between the terminal device 12 and thenetwork 2 or between network nodes 10 in the network 2. The followingsection provides some examples of how the identifier-to-index mappingcan be used.

Uses of WLAN identifiers In some implementations the terminal device 12or network node 10 will, when sending a message to another node (e.g.network node 10 or terminal device 12) in which a WLAN identifier shouldbe conveyed, include the index (or indices) associated with the WLANidentifier instead of e.g. reporting the identifier itself. For example,a terminal device 12 could be configured to report to the network theindices of WLANs for which one or more criteria are fulfilled. Examplecriteria can include:

-   -   A WLAN has been detected.    -   One or more measured signal metrics of a WLAN node 14 are above        (or below) thresholds.    -   The load and/or capacity of a WLAN node 14 is above (or below) a        threshold.

For example, the terminal device 12 can be configured to report to the3GPP RAN when it has detected WLAN APs with an SSID X, and the terminaldevice 12 would then report the index associated with SSID X, e.g. 3and/or D (as indicated in Example 1 above). In another example, theterminal device 12 may have measured (or received an indication of) thata WLAN with BSSID V has, for example, a load level below 40% and ameasured signal strength above 60 dBm, and the terminal device 12 wouldthen report index 2 and/or C (2 and C being the indices for BSSID V inExample 1).

One WLAN AP 14 can have identifiers of different types. For example, aWLAN AP 14 could have an SSID X and a BSSID U. In some implementations,the terminal device 12 will report the index associated with only oneidentifier associated with a WLAN. For example, if a WLAN node 14 hasSSID X with index 3 and has a BSSID U with index 1 the terminal device12 may be configured to only report either 3 or 1. Which of the multipleindices are to be reported may, for example, be decided based on thetype of identifiers. Since BSSIDs are of higher granularity (associatedwith a specific WLAN node 14) while SSIDs have lower granularity(associated with a group of WLAN APs 14) it would provide moreinformation to the network if the terminal device 12 reports that hasdetected a certain BSSID instead of detecting a certain SSID, i.e. theUE would in the example above report index ‘1’. It would also bepossible for the network to configure the terminal device 12 as to whichindex the terminal device 12 should apply. In an alternativeimplementation the terminal device 12 can report all applicable indicesfor a WLAN. Using the example above, the terminal device 12 would thenreport both indices ‘3’ and ‘1’.

In implementations where multiple WLANs share an index, it may be thecase that multiple WLANs that share an index meet the criteria forsending a measurement report, the terminal device 12 may include in thereport information related to one of the multiple WLANs. For example, ifthe terminal device 12 measures BSSID V and BSSID W and both fulfills acriterion for reporting, then the UE 12 may only include in the reportinformation/measurements relating to one of BSSID V and BSSID W. Whichof the multiple WLANs is included may be configured by the network, e.g.by an associated priority. Alternatively, in embodiments of thetechniques described herein, the terminal device 12 may decide which ofthe multiple WLANs (or rather the indices for the multiple WLANs) toinclude in the report. For example, the terminal device 12 may includethe WLAN which has e.g. the strongest signal, the highest signalquality, the lowest air interface load, the highest total capacity orthe highest current capacity, etc. It would also be possible for theterminal device to, based on one or more metrics, decide which of theWLANs is “best” by considering several metrics such as signal strengthand load.

A method of operating a terminal device according to the aboveembodiment is shown in FIG. 10. In step 251, one or more indices and amapping between the one or more indices and respective networkidentifiers are maintained (e.g. stored) in the terminal device 12 (forexample in memory unit 36), with two or more networks or network nodessharing the same index. In step 253 if the terminal device 12 is to takean action in respect of a network and/or network node having an indexshared with another network and/or network node, then the terminaldevice 12 determines which one of the two or more networks and/ornetwork nodes having the shared index the terminal device is to take theaction in respect of. As noted above, this determining can be based onwhich WLAN has the strongest signal, the highest signal quality, thelowest air interface load, the highest total capacity or the highestcurrent capacity, etc. In the above embodiments, the action comprisesthe sending of a report (e.g. a measurement report) to the network. Inthe embodiments below, the action can comprise accessing, steeringtraffic or aggregating carriers over the network or network node.

In some implementations, the terminal device 12 can indicate to thenetwork how many WLANs matching a certain index fulfill the reportingcondition. For example, if the conditions for reporting for BSSID U,BSSID V and BSSID W are fulfilled the terminal device 12 may reportindex 1 and index 2 (as in Example 1 above). But the terminal device 12may then according to this embodiment also indicate that there is onenode associated with index 1 for which the conditions are fulfilled, andtwo nodes associated with index 2 for which the conditions arefulfilled.

In some implementations, the network (e.g. 3GPP RAN) may indicate to theterminal device 12 that it is to perform a mobility-related proceduretowards a WLAN by signaling the associated index. A mobility-relatedprocedure may be one or many of measurement reporting, traffic steering,access selection, traffic aggregation, etc. Prior to this being done thenetwork would need to indicate the identifier to index mapping, asdiscussed above. For example, the network may indicate to the terminaldevice 12 that it is to steer traffic to a WLAN with index 1, and the UE12 would then (according to the example mapping in Example 1 above)steer traffic to the WLAN with BSSID U. If the network indicates to theterminal device 12 to aggregate traffic over WLAN (and 3GPP) with index2 then the UE 12 may aggregate traffic over WLAN with BSSID V or BSSID Wand over 3GPP.

In some embodiments, if the terminal device 12 is requested to performan action with respect to a WLAN with a certain index and the terminaldevice 12 finds multiple candidate WLANs with that index but is onlycapable of performing the action for one of (or a subset of) themultiple candidates, the terminal device 12 can decide which candidatesthe action should be performed for (step 253). For example, if theterminal device 12 is requested to steer traffic over a WLAN with index2 and the terminal device 12 finds both BSSID V and BSSID W (which bothhave index 2), the UE 12 may select one of the two BSSIDs to apply theaction to. As in the above embodiment, which of the multiple WLANs isselected may be determined based on a rule, for example the WLAN withthe strongest signal, the highest signal quality, the lowest load, etc.It would also be possible for the terminal device 12 to, based on one ormore metrics, decide which of the network nodes is “best” by consideringmetrics such as signal strength and load. In alternativeimplementations, the network can configure the terminal device 12 as towhich of the multiple candidates the terminal device 12 should performthe action for.

As noted above, it is also possible for the identifier-to-index mappingto be used in other messages/indications/procedures than those describedabove. For example, another use case for the identifier-to-index mappingis when the network indicates that a terminal device 12 should evaluatean access network selection, traffic steering and/or carrier aggregationmechanism considering only certain WLAN identifiers.

Indication of Whether to use Indices or Network Identifiers

Not all terminal devices, networks, or network nodes, may be capable ofusing indices instead of network identifiers. Therefore the networkcould, in some implementations, indicate to the terminal device 12whether to use indices or to use WLAN identifiers when referring toWLANs. For example, if an LTE eNB is capable of using indices instead ofWLAN identifiers, that eNB may indicate to the terminal devices 12 it isserving that signalling of indices should be used, while if another LTEeNB is not capable of using indices instead of WLAN identifiers thenthat eNB may indicate to the terminal device 12 that signalling of WLANidentifiers should be used.

The indication may be explicitly signalled by the network, for exampleas a bit-flag indication, which could be signalled using dedicatedsignalling or broadcast signalling. It may be the case that if thisbit-flag has not been signalled to the terminal device 12, the terminaldevice 12 would interpret this as the network indicating that indicesshould not be used.

In some implementations it is possible for this indication to besignalled implicitly. The terminal device 12 may consider that thenetwork has indicated that indices should be used if the network signalsindices together with the WLAN identifiers, while if the network has notindicated any indices with the WLAN identifiers, the terminal device 12would consider that the network has indicated that indices should not beused.

Subscription Based Identifier to Index Mapping

In some implementations the identifier-to-index mapping can be signaledto the terminal device 12 by a core network node 4, e.g. an MME. In someembodiments of the techniques described herein this core network node 4may consider information about the user subscription when determiningthe identifier-to-index mapping for a terminal device 12. For example,the core network node 4 may provide different index-to-identifiermappings to gold users (e.g. users with expensive or higher valuesubscriptions) than to bronze users (e.g. users with less expensive orlower value subscriptions). This means that, depending on thesubscription, the terminal devices 12 can be handled differently. Forexample, it will below be explained how a terminal device 12 reports toan RAN node 10 the index associated with a WLAN AP 14 (instead of theidentifier for the WLAN AP 14) when the terminal device 12 has detectedthe WLAN AP 14. If the identifier-to-index mapping has been setdifferently for terminal devices 12 based on the user subscriptions,then the RAN node 10 can take different approaches with respect toterminal devices 12 with different subscriptions without needing to knowthe subscription level.

In some embodiments, the RAN may apply different behaviors depending onthe index for a WLAN identifier. For example, the RAN may be configuredto apply a more aggressive offloading strategy towards WLANs with index1 compared to WLANs with index 2, i.e. traffic steering towards a WLANwith index 1 may be done at a lower 3GPP load level compared to trafficsteering towards a WLAN with index 2. Hence, with the subscription basedidentifier to index mapping it would be possible that the core networknode 4 (e.g. MME) has assigned index 1 for SSID X for a bronze userwhile assigning index 2 for SSID X for a gold user. This means that thebronze user will report index 1 when it detects a WLAN with SSID X, buta gold user will report index 2, and then the RAN may then offload thebronze user while keeping the gold user in 3GPP (assuming that the 3GPPnetwork is more likely provide a better user experience than WLAN).

Flow charts illustrating the above embodiments are shown in FIGS. 11 and12. FIG. 11 corresponds to a method of operating a network node (e.g. acore network node or a node in the RAN) that determines the indices andmapping. FIG. 12 corresponds to a method of operating a network node(e.g. a RAN node) that uses the indices and mapping in communicationswith a terminal device.

Thus, in step 261 of FIG. 11, the network node 6 determines one or moreindices and a mapping between the one or more indices and respectivenetwork identifiers, with different mappings being determined fordifferent terminal devices and/or network subscribers as describedabove. In step 263, the mappings and indices are sent to the relevantterminal devices and/or network subscribers for use in communicationsbetween the terminal device and the network.

In step 271 of FIG. 12, the network node maintains one or more indicesand one or more mappings between the one or more indices and respectivenetwork identifiers. Different mappings for different terminal devicesand/or network subscribers are maintained. In communications between thenetwork node and a terminal device in which a particular network or aparticular network node is to be identified, the network node uses theindex associated with the particular network or the particular networknode in the mapping that applies to the terminal device or itssubscriber to identify the particular network or the particular networknode (step 273).

Identifier Handling in Terminal Devices and the Network

In some embodiments the terminal device 12 and/or network may maintainthe WLAN identifiers in an array or table, as shown in Example 2 below.The WLAN identifiers would be placed at an entry in the array or tablecorresponding to the index of the identifier. E.g. if the index of SSIDX is 3 then SSID X would be placed in location 3 of the array. It wouldalso be possible for the indices to be offset by an integer, e.g. a WLANidentifier with index X is placed in location X+N where N is a positiveor negative integer value.

A method of operating a node in a network according to these embodimentsis shown in FIG. 13. The node can be a network node, such as a RAN node10 or a node 6 in the core network, or a terminal device 12. In step281, the node maintains one or more indices and a mapping between theone or more indices and respective network identifiers in an array or atable (with each network identifier identifying a network or a networknode). Then, in communications between the node and another node in thefirst network in which a particular network and/or a particular networknode is to be identified, the index associated with the particularnetwork and/or the particular network node is used to identify theparticular network and/or the particular network node (step 283).

When the terminal device 12 is going to scan for/start reportingfor/steer traffic to a WLAN with an index X, the UE would scan for/startreporting for/steer traffic to the corresponding WLANs which are placedat entry X in the array.

Example 2: WLAN identifiers in an array 0 1 BSSID U 2 BSSID V, BSSID W 3SSID X 4 5 6 SSID Y 7

In case there are multiple identifiers associated with the same indexthe terminal device 12 may represent this using a two dimensional arraywhere there is a list of identifiers in each array entry.

Specific Embodiment

The flow chart in FIG. 14 illustrates a specific embodiment of thetechniques described herein in which an identifier to index mapping isused in a traffic steering command based approach to an access networkselection and/or traffic steering. The steps shown in FIG. 14 coversteps performed in both the terminal device and the network (e.g. RAN)node.

Thus, in step 301 a terminal device 12 receives a WLAN identifier toindex mapping over broadcast signalling from an eNB 10. The terminaldevice 12 maintains the mapping in an array (step 303), for example bystoring it in a memory unit.

As part of an access network selection and/or traffic steeringprocedure, the terminal device 12 is requested by the eNB 10 to performmeasurement reporting of a WLAN with an index X (step 305).

The terminal device 12 extracts the WLAN identifier(s) associated withindex X from the array (step 307) and performs measurements of WLANshaving identifier(s) matching the extracted identifier(s) (step 309).

The terminal device 12 constructs a measurement report and indicates theindices for the measured WLANs in the report (step 311). The report issent to the eNB 10.

The network (eNB 10) receives the measurement report (step 313).

The network extracts from the identifier to index mapping the WLANidentifiers corresponding to the indices in the received report (step315).

The network then evaluates whether the terminal device 12 should steertraffic to the reported WLANs and if so to which WLAN (step 317). If notraffic steering is to be performed, the method ends (steps 319 and321). If traffic steering is to be performed, the network indicates tothe terminal device 12 that traffic steering should be performed (via atraffic steering command) and includes the index of the WLAN to whichtraffic should be steered (step 323).

The terminal device 12 receives the indication (traffic steeringcommand) and extracts the WLAN identifier associated with the indicatedindex from the identifier to index mapping (step 325). The terminaldevice 12 then performs the traffic steering to the appropriate WLAN(step 327).

Modifications and other variants of the described embodiment(s) willcome to mind to one skilled in the art having the benefit of theteachings presented in the foregoing descriptions and the associateddrawings. Therefore, it is to be understood that the embodiment(s)is/are not to be limited to the specific examples disclosed and thatmodifications and other variants are intended to be included within thescope of this disclosure. Although specific terms may be employedherein, they are used in a generic and descriptive sense only and notfor purposes of limitation.

Various exemplary embodiments of the techniques described herein are setout below:

1. A method of operating a terminal device in a first network, themethod comprising:

-   -   maintaining one or more indices and a mapping between the one or        more indices and respective network identifiers, each network        identifier identifying a network or a network node, wherein two        or more networks or network nodes share the same index; and    -   in the event that the terminal device is to take an action in        respect of a network or network node having an index shared with        another network or network node, the method further comprises        the step of:    -   determining which one of the two or more networks or network        nodes having the shared index the terminal device is to take the        action in respect of.

2. A method as in embodiment 1, wherein the action comprises sending areport to the first network.

3. A method as in embodiment 2, wherein the report is a reportindicating one or more measurements of the determined network or networknode.

4. A method as in embodiment 3, wherein the action comprises sending areport to the first network in respect of a network or network node forwhich one or more criteria are fulfilled.

5. A method as in embodiment 4, wherein two or more of the networks ornetwork nodes having a shared index fulfil the criteria, and wherein thestep of determining comprises determining which one of the two or morenetworks or network nodes the report should include the one or moremeasurements for.

6. A method as in any of embodiments 1-5, wherein the step ofdetermining is performed in the event that the terminal device receivesan index from the first network that is shared by two or more networksor network nodes.

7. A method as in embodiment 6, wherein the index is received from thefirst network with an indication of an action the terminal device is totake with respect to a network or network node associated with theindex.

8. A method as in embodiment 7, wherein the action the terminal deviceis to take is to access, steer traffic and/or aggregate traffic to anetwork or network node associated with the index.

9. A method as in any of embodiments 1-8, wherein the step ofdetermining comprises determining the network or network node having theshared index to take the action in respect of as the network or networknode that has any one or more of:

-   -   (i) the strongest signal;    -   (ii) the highest signal quality;    -   (iii) the lowest air interface load;    -   (iv) the highest total capacity; and    -   (v) the highest current capacity.

10. A method as in any of embodiments 1-9, wherein the action is part ofan access network selection, traffic steering and/or traffic aggregationmechanism.

11. A terminal device for use in a first network, the terminal devicebeing adapted to:

-   -   maintain one or more indices and a mapping between the one or        more indices and respective network identifiers, each network        identifier identifying a network or a network node, wherein two        or more networks or network nodes share the same index; and    -   determine which one of the two or more networks or network nodes        having the shared index the terminal device is to take an action        in respect of in the event that the terminal device is to take        an action in respect of a network or network node having an        index shared with another network or network node.

Various other embodiments of the terminal device are contemplated inwhich the terminal device is further adapted to operate according to anyof the above method embodiments.

12. A method of operating a node in a first network, the methodcomprising:

-   -   maintaining one or more indices and a mapping between the one or        more indices and respective network identifiers in an array or a        table, each network identifier identifying a network or a        network node; and    -   in communications between the node and another node in the first        network in which a particular network or a particular network        node is to be identified, using the index associated with the        particular network or the particular network node to identify        the particular network or the particular network node.

13. A method as in embodiment 12, wherein the step of maintainingcomprises placing each network identifier at an entry in the array ortable corresponding to the respective index for the network identifier.

14. A method as in embodiment 12, wherein the step of maintainingcomprises placing each network identifier at an entry in the array ortable that is offset from the respective index for the networkidentifier.

15. A method as in embodiment 12, 13 or 14, wherein two or more networksor network nodes share the same index and the array is a two-dimensionalarray.

16. A method as in any of embodiments 12-15, wherein the node is aterminal device.

17. A method as in any of embodiments 12-15, wherein the node is anetwork node in the first network.

18. A node for use in a first network, the node being adapted to:

-   -   maintain one or more indices and a mapping between the one or        more indices and respective network identifiers in an array or a        table, each network identifier identifying a network or a        network node; and    -   use the index associated with the particular network or the        particular network node to identify the particular network or        the particular network node in communications between the node        and another node in the first network in which a particular        network or a particular network node is to be identified.

Various other embodiments of the node are contemplated in which the nodeis further adapted to operate according to any of the above methodembodiments.

19. A method of operating a network node in a first network, the methodcomprising:

-   -   determining one or more indices and a mapping between the one or        more indices and respective network identifiers, each network        identifier identifying a network or a network node, wherein        different mappings are determined for different terminal devices        and/or network subscribers; and    -   sending the one or more indices and the mapping to another        network node in the first network or to a terminal device in the        first network.

20. A method as in embodiment 19, wherein the step of determiningcomprises determining a first mapping for terminal devices and/ornetwork subscribers having a first subscription level and determining asecond mapping for terminal devices and/or network subscribers having asecond subscription level.

21. A network node for use in a first network, the network node beingadapted to

-   -   determine one or more indices and a mapping between the one or        more indices and respective network identifiers, each network        identifier identifying a network or a network node, wherein        different mappings are determined for different terminal devices        and/or network subscribers; and    -   send the one or more indices and the mapping to another network        node in the first network or to a terminal device in the first        network.

Various other embodiments of the network node are contemplated in whichthe network node is further adapted to operate according to any of theabove method embodiments.

21. A method of operating a network node in a first network, the methodcomprising:

-   -   maintaining one or more indices and one or more mappings between        the one or more indices and respective network identifiers, each        network identifier identifying a network or a network node,        wherein different mappings apply to different terminal devices        and/or network subscribers; and    -   in communications between the network node and a terminal device        in which a particular network or a particular network node is to        be identified, using the index associated with the particular        network or the particular network node in the mapping that        applies to the terminal device to identify the particular        network or the particular network node.

22. A method as in embodiment 21, wherein the communications between thenetwork node and the terminal device comprise communications relating toan access network selection, traffic steering and/or traffic aggregationmechanism.

23. A method as in embodiment 22, further comprising the step of:

-   -   determining an action for the terminal device to take in respect        of the particular network or particular network node, the action        for the terminal device to take being determined based on an        index for the particular network or particular network node        received from the terminal device.

24. A network node for use in a first network, the network node beingadapted to:

-   -   maintain one or more indices and one or more mappings between        the one or more indices and respective network identifiers, each        network identifier identifying a network or a network node,        wherein different mappings apply to different terminal devices        and/or network subscribers; and    -   use the index associated with the particular network or the        particular network node in the mapping that applies to a        terminal device to identify a particular network or a particular        network node in communications between the network node and the        terminal device in which the particular network or the        particular network node is to be identified.

Various other embodiments of the network node are contemplated in whichthe network node is further adapted to operate according to any of theabove method embodiments.

In any of the above embodiments each network identifier can identify anetwork other than the first network or a network node in a networkother than the first network. In some embodiments, the network otherthan the first network is a network that is operating according to adifferent radio access technology, RAT, to the first network.

In any of the above embodiments the first network is a network operatingaccording to a mobile telecommunications radio access technology, RAT,and the particular network or the particular network node are operatingaccording to a wireless local area network RAT. In some embodiments themobile telecommunications RAT is a 3GPP-specified RAT. In someembodiments the wireless local area network RAT is WLAN or Wi-Fi.

In any of the above embodiments each network identifier can be anidentifier of a WLAN or a network node in a WLAN.

In any of the above embodiments at least one network identifier can bean identifier for an access point, AP, in a WLAN.

In any of the above embodiments at least one network identifier can be aservice set identification, SSID, a basic SSID, BSSID, an extended SSID,ESSID, a homogenous ESSID, HESSID, Realm identifier, a Network AccessIndicator, NAI, a public land mobile network, PLMN identifier, or aDomain Name list.

In any of the above embodiments each index can comprise a numericalvalue or an alphanumerical value.

In any of the above embodiments the index can be signalled using apriority value in communications between nodes.

In any of the above embodiments a default value for an index can be usedin communications for a network identifier that is not included in themapping.

In any of the above embodiments two or more networks or network nodescan have the same index. In some embodiments, in the event that at leastone of the networks or network nodes having the same index is to beidentified in communications, the communications further comprise anindication of how many of said networks or network nodes having the sameindex the communications apply to.

In any of the above embodiments a network identifier can have two ormore associated indices.

In any of the above embodiments, a particular network or a particularnetwork node can have two or more associated network identifiers, eachnetwork identifier having a respective index, and in communications inwhich the particular network or particular network node having the twoor more associated network identifiers is to be identified, the one ormore of the indices can be used to identify the particular network orthe particular network node. In some embodiments the two or moreassociated network identifiers are different types of networkidentifiers, and an index for a specific type of network identifier canbe used to identify the particular network or the particular networknode.

In any of the above embodiments, the indices and mapping are used incommunications relating to an access network selection, traffic steeringand/or traffic aggregation procedure.

In any of the above embodiments the indices and mapping are used incommunications relating to an access network selection, traffic steeringand/or traffic aggregation procedure between the first network and asecond network operating according to a different radio accesstechnology, RAT, to the first network. In some embodiments each networkidentifier identifies a particular second network or a particularnetwork node in the second network.

There is also provided a computer program product comprising a computerreadable medium having computer readable code embodied therein, thecomputer readable code being configured such that, on execution by asuitable computer or processor, the computer or processor is caused toperform any of the method embodiments described above.

1. A method of operating a terminal device in a first network, themethod comprising: maintaining one or more indices and a mapping betweenthe one or more indices and respective network identifiers, each networkidentifier identifying a network and/or a network node, wherein two ormore networks and/or network nodes share the same index; and in theevent that the terminal device is to take an action in respect of anetwork and/or network node having an index shared with another networkand/or network node, the method further comprises the step of:determining which one of the two or more networks and/or network nodeshaving the shared index the terminal device is to take the action inrespect of.
 2. The method as in claim 1, wherein the action comprisessending a report to the first network.
 3. The method as in claim 2,wherein the report is a report indicating one or more measurements ofthe determined network and/or network node.
 4. The method as in claim 3,wherein the action comprises sending a report to the first network inrespect of a network and/or network node for which one or more criteriaare fulfilled.
 5. The method as in claim 4, wherein two or more of thenetworks and/or network nodes having a shared index fulfil the criteria,and wherein the step of determining comprises determining which one ofthe two or more networks and/or network nodes the report should includethe one or more measurements for.
 6. The method as in claim 1, whereinthe step of determining is performed in the event that the terminaldevice receives an index from the first network that is shared by two ormore networks and/or network nodes.
 7. The method as in claim 6, whereinthe index is received from the first network with an indication of anaction the terminal device is to take with respect to a network and/ornetwork node associated with the index.
 8. The method as in claim 7,wherein the action the terminal device is to take is to access, steertraffic and/or aggregate traffic to a network and/or network nodeassociated with the index.
 9. The method as in claim 1, wherein the stepof determining comprises determining the network and/or network nodehaving the shared index to take the action in respect of as the networkand/or network node that has any one or more of: (i) the strongestsignal; (ii) the highest signal quality; (iii) the lowest air interfaceload; (iv) the highest total capacity; and (v) the highest currentcapacity.
 10. The method as in claim 1, wherein the action is part of anaccess network selection, traffic steering and/or traffic aggregationmechanism.
 11. A terminal device for use in a first network, theterminal device being adapted to: maintain one or more indices and amapping between the one or more indices and respective networkidentifiers, each network identifier identifying a network and/or anetwork node, wherein two or more networks and/or network nodes sharethe same index; and determine which one of the two or more networksand/or network nodes having the shared index the terminal device is totake an action in respect of in the event that the terminal device is totake an action in respect of a network and/or network node having anindex shared with another network and/or network node.
 12. The terminaldevice as in claim 11, wherein two or more of the networks and/ornetwork nodes having a shared index fulfil the criteria, and wherein theterminal device is adapted to determine which one of the two or morenetworks and/or network nodes the report should include the one or moremeasurements for.
 13. The terminal device as in claim 11, wherein theterminal device is adapted to determine which one of the two or morenetworks and/or network nodes having the shared index the terminaldevice is to take an action in respect of in the event that the terminaldevice receives an index from the first network that is shared by two ormore networks and/or network nodes.
 14. The terminal device as in claim13, wherein the index is received from the first network with anindication of an action the terminal device is to take with respect to anetwork and/or network node associated with the index.
 15. The terminaldevice as in claim 14, wherein the action the terminal device is to takeis to access, steer traffic and/or aggregate traffic to a network and/ornetwork node associated with the index.
 16. A terminal device as inclaim 11, wherein the terminal device is adapted to determine thenetwork and/or network node having the shared index to take the actionin respect of as the network and/or network node that has any one ormore of: (i) the strongest signal; (ii) the highest signal quality;(iii) the lowest air interface load; (iv) the highest total capacity;and (v) the highest current capacity.
 17. The terminal device as inclaim 11, wherein the action is part of an access network selection,traffic steering and/or traffic aggregation mechanism.
 18. A method ofoperating a node in a first network, the method comprising: maintainingone or more indices and a mapping between the one or more indices andrespective network identifiers in an array or a table, each networkidentifier identifying a network and/or a network node; and incommunications between the node and another node in the first network inwhich a particular network and/or a particular network node is to beidentified, using the index associated with the particular networkand/or the particular network node to identify the particular networkand/or the particular network node.
 19. The method as in claim 18,wherein the step of maintaining comprises placing each networkidentifier at an entry in the array or table corresponding to therespective index for the network identifier.
 20. The method as in claim18, wherein the step of maintaining comprises placing each networkidentifier at an entry in the array or table that is offset from therespective index for the network identifier.
 21. The method as in claim18, wherein two or more networks and/or network nodes share the sameindex and the array is a two-dimensional array.
 22. The method as inclaim 18, wherein the node is a terminal device.
 23. A method as inclaim 18, wherein the node is a network node in the first network.
 24. Anode for use in a first network, the node being adapted to: maintain oneor more indices and a mapping between the one or more indices andrespective network identifiers in an array or a table, each networkidentifier identifying a network and/or a network node; and use theindex associated with the particular network and/or the particularnetwork node to identify the particular network and/or the particularnetwork node in communications between the node and another node in thefirst network in which a particular network and/or a particular networknode is to be identified.
 25. The node as in claim 24, wherein the nodeis adapted to maintain one or more indices and a mapping between the oneor more indices and respective network identifiers by placing eachnetwork identifier at an entry in the array or table corresponding tothe respective index for the network identifier.
 26. The node as inclaim 24, wherein the node is adapted to maintain one or more indicesand a mapping between the one or more indices and respective networkidentifiers by placing each network identifier at an entry in the arrayor table that is offset from the respective index for the networkidentifier.
 27. The node as in claim 24, wherein the node is a terminaldevice.
 28. The node as in claim 24, wherein the node is a network nodein the first network.
 29. A method of operating a network node in afirst network, the method comprising: determining one or more indicesand a mapping between the one or more indices and respective networkidentifiers, each network identifier identifying a network and/or anetwork node, wherein different mappings are determined for differentterminal devices and/or network subscribers; and sending the one or moreindices and the mapping to another network node in the first network orto a terminal device in the first network.
 30. The method as in claim29, wherein the step of determining comprises determining a firstmapping for terminal devices and/or network subscribers having a firstsubscription level and determining a second mapping for terminal devicesand/or network subscribers having a second subscription level.
 31. Anetwork node for use in a first network, the network node being adaptedto: determine one or more indices and a mapping between the one or moreindices and respective network identifiers, each network identifieridentifying a network and/or a network node, wherein different mappingsare determined for different terminal devices and/or networksubscribers; and send the one or more indices and the mapping to anothernetwork node in the first network or to a terminal device in the firstnetwork.
 32. The network node as in claim 31, wherein the network nodeis adapted to determine one or more indices and a mapping between theone or more indices and respective network identifiers by determining afirst mapping for terminal devices and/or network subscribers having afirst subscription level and determining a second mapping for terminaldevices and/or network subscribers having a second subscription level.33. A method of operating a network node in a first network, the methodcomprising: maintaining one or more indices and one or more mappingsbetween the one or more indices and respective network identifiers, eachnetwork identifier identifying a network and/or a network node, whereindifferent mappings apply to different terminal devices and/or networksubscribers; and in communications between the network node and aterminal device in which a particular network and/or a particularnetwork node is to be identified, using the index associated with theparticular network and/or the particular network node in the mappingthat applies to the terminal device to identify the particular networkand/or the particular network node.
 34. The method as in claim 33,wherein the communications between the network node and the terminaldevice comprise communications relating to an access network selection,traffic steering and/or traffic aggregation mechanism.
 35. The method asin claim 34, further comprising the step of: determining an action forthe terminal device to take in respect of the particular network and/orparticular network node, the action for the terminal device to takebeing determined based on an index for the particular network and/orparticular network node received from the terminal device.
 36. A networknode for use in a first network, the network node being adapted to:maintain one or more indices and one or more mappings between the one ormore indices and respective network identifiers, each network identifieridentifying a network and/or a network node, wherein different mappingsapply to different terminal devices and/or network subscribers; and usethe index associated with the particular network and/or the particularnetwork node in the mapping that applies to a terminal device toidentify a particular network and/or a particular network node incommunications between the network node and the terminal device in whichthe particular network and/or the particular network node is to beidentified.
 37. The network node as in claim 36, wherein thecommunications between the network node and the terminal device comprisecommunications relating to an access network selection, traffic steeringand/or traffic aggregation mechanism.
 38. The network node as in claim37, wherein the network node is further adapted to: determine an actionfor the terminal device to take in respect of the particular networkand/or particular network node, the action for the terminal device totake being determined based on an index for the particular networkand/or particular network node received from the terminal device.
 39. Acomputer program product comprising a computer readable medium havingcomputer readable code embodied therein, the computer readable codebeing configured such that, on execution by a suitable computer orprocessor, the computer or processor is caused: maintain one or moreindices and a mapping between the one or more indices and respectivenetwork identifiers, each network identifier identifying a networkand/or a network node, wherein two or more networks and/or network nodesshare the same index; and in the event that the terminal device is totake an action in respect of a network and/or network node having anindex shared with another network and/or network node, determine whichone of the two or more networks and/or network nodes having the sharedindex the terminal device is to take the action in respect of.